Applications of multicolor technology based on color conversion methods to liquid crystal displays, organic EL displays, lighting, and the like have been actively studied. The color conversion means that light emitted from a light emitter is converted into light having a longer wavelength, and, for example, refers to converting blue light emission into green light emission or red light emission. By forming this composition having a color conversion function into a film and combining the film with, for example, a blue light source, three primary colors of blue, green, and red can be extracted from the blue light source, that is, white light can be extracted. A white light source formed by combining such a blue light source and a film having the color converting function is used as a backlight unit and this backlight unit, a liquid crystal driving portion, and a color filter are combined, whereby a full color display can be produced. In addition, when no liquid crystal driving part is included, the backlight unit can be used as it is as a white light source and can be applied as a white light source such as LED illumination.
Examples of a problem of the liquid crystal display include improvement of color reproducibility. In order to improve the color reproducibility, increase in color purity of each color of blue, green, and red by narrowing half width of each light emission spectrum of blue, green, and red of the backlight unit is effective. As a means for solving this problem, a technique of using quantum dots of inorganic semiconductor fine particles as a component of a color conversion composition has been proposed (refer to Patent Literature 1, for example). In the technique of using these quantum dots, the half widths of the light emission spectra of green and red are certainly narrow and the color reproducibility is improved. On the other hand, the quantum dots are weak against heat, and moisture and oxygen in the air and thus durability has been insufficient.
In addition, a technique of using an organic light emitting material as a component of a color conversion composition instead of the quantum dots has also been developed. Disclosed examples of the techniques using the organic light emitting material as the component of the color conversion composition include a technique using a pyridine-phthalimide condensation derivative (refer to Patent Literature 2, for example), a technique using a coumarin compound (refer to Patent Literature 3, for example), a technique using a perylene derivative as a red light emitting material (refer to Patent Literature 4, for example), a technique using a rhodamine-based compound (refer to Patent Literature 5, for example), and a technique using a pyrromethene compound (refer to Patent Literatures 6 and 7, for example).